The rapidly expanding Corps of Engineers, activated the 340th Regiment at Vancouver Barracks in March of 1942, ‘seeding it’ with a small cadre of officers from the 18th Combat Engineer Regiment.
On March 9, sixty-two enlisted men from Fort Francis E. Warren joined them and in short order several hundred more arrived from Fort Leonard Wood. By April 1 Colonel Russell Lyons, their commander, had a full complement of officers and men, and the 340th was already loading supplies and what equipment they had for shipment north.